Patent Grant
7448710
1. Field of the Invention
The present invention relates to a liquid droplet ejection head and an image forming apparatus, and more particularly, to a structure of a liquid droplet ejection head in which a plurality of liquid droplet ejection ports (nozzles) are arranged two-dimensionally at high density, and an image forming apparatus which forms an image on a recording medium by means of liquid droplets ejected from the liquid droplet ejection head.
2. Description of the Related Art
Japanese Patent Application Publication No. 4-329151 describes a recording apparatus having a recording head which combines a spray mechanism for white ink only, which uses a piezoelectric element, and a spray mechanism for a dye sublimation coloring material, which uses a heat generating resistance element. This recording apparatus forms colored ink by causing white ink and coloring material sprayed from the recording head to collide with each other during flight, in such a manner that recording is performed by means of the colored ink landing on a recording medium.
Although Japanese Patent Application Publication No. 4-329151 discloses a structure of a recording head comprising a spray mechanism using a piezoelectric element and a spraying mechanism using a heat generating resistance element, it does not describe a high-density arrangement of ejection ports or pressure chambers.
In general, the ejection method using piezoelectric elements (a “piezo” method) has the merit of allowing a great deal of freedom in the selection of the material of the ejection liquid; however, the piezoelectric elements and pressure chambers are large in size, and in the case of a head composition which ejects two liquids, it is difficult to achieve a high-density arrangement of the pressure chambers.
As opposed to this, a method (thermal method) which heats a liquid by means of a heat-generating element and ejects the liquid by means of the gas bubbles formed by film boiling makes it relatively easier to achieve high density, compared to the piezo method described above; however, since it is necessary to boil the ejection liquid, the amount of freedom in selecting the ejection liquid is reduced.
Japanese Patent Application Publication No. 10-24564 discloses a method and structure of an ejection head for achieving same, whereby two types of liquids, which are reactive, are combined within the head and are ejected from ejection ports, recording being performed by means of the ejected liquid landing on a recording medium.
However, since the two types of reactive liquid are combined inside a flow channel connected to an ejection port (nozzle), there is a possibility that blockages may occur due to the combined reaction of the two liquids. Hence, from the viewpoint of avoiding blockages of this kind, a method is desired in which the two liquids are combined after ejection.
The present invention has been contrived with the foregoing circumstances in view, an object thereof being to provide a structure of a liquid droplet ejection head, and an image forming apparatus using this liquid droplet ejection head, whereby a method which combines two liquids after ejection can be adopted, while also using a piezo method which allows high freedom of selection of the ejection liquid, and allowing a high density arrangement of the pressure chambers.
In order to attain the aforementioned object, the present invention is directed to a liquid droplet ejection head, comprising: first nozzles which eject droplets of a first liquid to an ejection receiving medium; second nozzles which eject droplets of a second liquid to the ejection receiving medium; first pressure chambers which are connected to the first nozzles and filled with the first liquid to be ejected from the first nozzles; first pressure generating devices which cause the first liquid to be ejected from the first nozzles by applying pressure to the first liquid inside the first pressure chambers; second pressure chambers which are connected to the second nozzles and filled with the second liquid to be ejected from the second nozzles; and second pressure generating devices which cause the second liquid to be ejected from the second nozzles by applying pressure to the second liquid inside the second pressure chambers, wherein the first nozzles and the second nozzles are arranged in a two-dimensional array and disposed adjacently in mutual proximity so as to be aligned in a sub-scanning direction which is parallel to a relative direction of movement of the ejection receiving medium and the liquid droplet ejection head, in such a manner that the first liquid and the second liquid ejected respectively from the first nozzle and the second nozzle that are arranged in mutual proximity are deposited at substantially same position on the ejection receiving medium.
According to the present invention, the first liquid filled into the first pressure chambers is ejected from the first nozzles by means of the pressure generated by the first pressure generating devices. Similarly, the second liquid filled into the second pressure chambers is ejected from the second nozzles by means of the pressure generated by the second pressure generating devices. The first liquid and the second liquid ejected respectively from a first nozzle and a second nozzle which are positioned adjacently in mutual proximity on the same line in the sub-scanning direction, which is parallel to the relative movement direction of the ejection receiving medium with respect to the liquid droplet ejection head, are deposited in substantially the same position on the ejection receiving medium, and the two liquids mix together.
More specifically, according to the present invention, a high-density nozzle arrangement is possible, and it is possible for the two liquids to mix together on the ejection receiving medium after the two liquids have been ejected. Furthermore, in the present invention, it is possible to use an actuator such as a piezoelectric element in the first pressure generating device and the second pressure generating device, and hence the freedom of selection of the ejection liquid is increased.
Preferably, the first pressure chambers and the second pressure chambers are formed to have an approximately square planar shape; each of the first pressure chambers has a nozzle connection port for directing the first liquid to the first nozzle, and a supply port for introducing the first liquid into the first pressure chamber, the nozzle connection port and the supply port being disposed on a diagonal of the approximately square planar shape; and each of the second pressure chambers has a nozzle connection port for directing the second liquid to the second nozzle, and a supply port for introducing the second liquid into the second pressure chamber, the nozzle connection port and the supply port being disposed on a diagonal of the approximately square planar shape.
By adopting a substantially square planar shape for the first pressure chambers and second pressure chambers, the deformation efficiency of the first pressure generating device and the second pressure generating device which cause displacement of the approximately square-shaped pressure chamber surface is improved. Furthermore, by arranging the nozzle connection port and the supply port on a diagonal of a substantially square-shaped pressure chamber, the liquid becomes less liable to stagnate within the pressure chamber and air bubble expulsion properties are improved.
Preferably, a first nozzle inclination angle which defines a direction of ejection of the first liquid from the first nozzles, and a second nozzle inclination angle which defines a direction of ejection of the second liquid from the second nozzles are set in such a manner that the droplet of the first liquid ejected from the first nozzle and the droplet of the second liquid ejected from the second nozzle are propelled toward substantially the same position on the ejection receiving medium.
By means of this composition, two types of liquid droplets can be made to land substantially simultaneously at substantially the same position on the ejection receiving medium. Here, “substantially the same position” means a positional relationship whereby the first liquid droplet and the second liquid droplet landing on the ejection receiving medium are able to make contact, coalesce and combine with each other.
Preferably, the first pressure chambers and the second pressure chambers are arranged in a layered structure, in such a manner that the first pressure chambers and the second pressure chambers in different layers partially overlap with each other and non-overlapping regions thereof are aligned in the sub-scanning direction.
An even higher density nozzle pitch can be achieved by arranging the pressure chambers in a layered structure of this kind.
Preferably, the liquid droplet ejection head further comprises: a nozzle plate in which the first nozzles and the second nozzles are formed, wherein the first liquid having a relatively high viscosity is filled into the first pressure chambers formed in a layer which is nearer to the nozzle plate, and the second liquid having a relatively low viscosity is filled into the second pressure chambers formed in a layer which is further from the nozzle plate.
Focusing on the nozzle side flow channels leading from the pressure chambers to the nozzles, the flow channel resistance of the nozzle side flow channels from the first pressure chambers which are nearer to the nozzle plate is less than the flow channel resistance of the nozzle side flow channels leading from the second pressure chambers which are further from the nozzle plate. Therefore, high-viscosity liquid can be ejected readily by filling a first liquid of high viscosity into the first pressure chambers in the layer nearer the nozzle plate. The connecting sections between the nozzle side flow channels and the pressure chambers correspond to “nozzle connection ports”.
Preferably, a cross-sectional area and length of first nozzle side flow channels leading from the first pressure chambers to the first nozzles, and a cross-sectional area and length of second nozzle side flow channels leading from the second pressure chambers to the second nozzles are set in such a manner that a ratio between an ejected volume of the first liquid ejected from the first nozzles and an ejected volume of the second liquid ejected from the second nozzles is a prescribed value.
For example, the shapes of the respective nozzle side flow channels are designed in such a manner that the ratio of the ejection amounts is a prescribed value, if the same drive signal is applied to the first pressure generating device and the second pressure generating device. Thereby, it is possible to achieve a composition in which a common drive waveform is used for the first nozzles and the second nozzles.
Preferably, the first nozzles and the second nozzles are arranged two-dimensionally so as to be aligned in a row direction which is substantially parallel to a main scanning direction that is perpendicular to the relative direction of movement of the ejection receiving medium and the liquid droplet ejection head, and in a column direction which extends substantially in the sub-scanning direction, being oblique to the row direction at a prescribed angle; and a first common flow channel which supplies the first liquid to the first pressure chambers corresponding to the first nozzles aligned in the column direction, and a second common flow channel which supplies the second liquid to the second pressure chambers corresponding to the second nozzles aligned in the column direction, are formed in line with nozzle rows aligned in the column direction.
The nozzle rows extending in substantially the sub-scanning direction form a dot column (dot lines) in a line extending in the main scanning direction on the main scanning direction, by being driven (performing ejection) successively from one end of the nozzle row to the other end thereof, in conjunction with the relative movement of the ejection receiving medium. When driving the nozzles to forming a dot line in this way (namely, when performing main scanning), by arranging the first common flow channel and the second common flow channel in line with the nozzle rows extending substantially in the sub-scanning direction, it is possible to prevent concentration of load on one particular common flow channel during the ejection operation, and it is also possible to improve refilling characteristics.
Preferably, a first common flow channel which supplies the first liquid to the first pressure chambers and a second common flow channel which supplies the second liquid to the second pressure chambers are arranged in a layered structure, in such a manner that the first common flow channel and the second common flow channel in different layers partially overlap with each other.
By adopting a composition in which the first common flow channel and the second common flow channels are arranged in a layered fashion, it is possible to achieve even higher density.
Preferably, the first liquid contains a coloring material, and the second liquid contains at least one of a fixing reaction promoting agent and a permeation retarding agent.
If a fixing reaction promoting agent is used as the second liquid, then the fixing reaction proceeds rapidly after deposition of the liquids, and hence colors bleeding or landing interference can be prevented. Furthermore, if a permeation retarding agent is used as the second liquid, then permeation of the first liquid into the ejection receiving medium after landing thereon is impeded by the action of the permeation retarding agent. In other words, colors bleeding is prevented since the permeation rate is reduced during fixing.
Preferably, of the first nozzle and the second nozzle which are disposed in a mutually proximate arrangement, the first nozzle is disposed on a downstream side and the second nozzle is disposed on an upstream side in the relative movement direction of the ejection receiving medium with respect to the liquid droplet ejection head.
By adopting this arrangement, the second liquid (fixing reaction promoting agent or permeation retarding agent) ejected from the second nozzle is deposited firstly onto the ejection receiving medium, whereupon, at a slight time difference thereafter, the first liquid is deposited onto the ejection receiving medium. Therefore, the first liquid containing a coloring material does not land directly on the ejection receiving medium, and therefore, bleeding can be prevented reliably.
Preferably, the second nozzles are arranged in fewer number than the first nozzles, at a prescribed ratio with respect to the first nozzles.
For example, there is a composition in which second nozzles are arranged at every alternate row in the matrix array. By reducing the number of second nozzles, second pressure chambers, and the like, by a uniform ratio, it is possible to simplify manufacture and to reduce costs.
Preferably, a diameter of a dot formed by the droplet of the second liquid ejected from the second nozzle and deposited on the ejection receiving medium is set to a value whereby the dot has a surface area covering a region of a plurality of dots formed by the droplets of the first liquid which are ejected from the first nozzles that are mutually adjacent in a main scanning direction perpendicular to the relative movement direction of the ejection receiving medium and the liquid droplet ejection head, and deposited adjacently on the ejection receiving medium in an alignment in the main scanning direction.
In the case of a composition where the number of second nozzles is lower than the number of first nozzles, desirably, the second nozzles form dots of a size which is greater than the region of the dots formed by a plurality of first nozzles, in such a manner that the region of the dots formed by a plurality of first nozzles is covered by one second nozzle.
Preferably, a second nozzle inclination angle which defines a direction of ejection of the second liquid from the second nozzles is set in such a manner that the droplet of the second liquid ejected from the second nozzle is deposited in an approximately central position between two dots which are formed by two droplets of the first liquid ejected from the first nozzles that are mutually adjacent in the main scanning direction, and deposited adjacently on the ejection receiving medium in an alignment in the main scanning direction.
Thereby, it is possible to form the dots created by the second liquid to the minimum necessary size, and hence the amount of second liquid consumed can be reduced.
Preferably, within each of the plurality of dot regions, ejection of the droplet from the second nozzle is controlled in such a manner that the dot is formed by the second liquid only in cases where at least one dot is formed by the first nozzle.
The second liquid has a prescribed role when combined with the first liquid (for instance, promoting a fixing reaction, slowing the permeation rate, or the like), and hence there is no need to deposit the second liquid only in cases where no droplets of the first liquid are to be ejected. Therefore, by avoiding wasteful ejection of the second liquid and ejecting the second liquid only when it is necessary in relation to ejection of droplets of the first liquid, it is possible to reduce the amount of the second liquid consumed.
Preferably, the liquid droplet ejection head further comprises a mixture preventing device which prevents mixing of the first liquid and the second liquid, the mixture preventing device being arranged on an ejection surface on which the first nozzles and the second nozzles are formed, between the first nozzles and the second nozzles.
For the mixture prevention device, it is possible to adopt, for example, a groove, a dividing member, surface processing, or a combination of these. By adopting a mixture preventing device of this kind, it is possible to prevent liquid (first liquid or second liquid) that has adhered to the ejection surface of the liquid droplet ejection head from being transmitted over the ejection surface in such a manner that it enters into the orifice of a nozzle which ejects the other type of liquid.
In order to attain the aforementioned object, the present invention is also directed to an image forming apparatus, comprising: the above-described liquid droplet ejection head; a first liquid supply device which supplies the first liquid to the liquid droplet ejection head; a second liquid supply device which supplies the second liquid to the liquid droplet ejection head; a conveyance device which performs a relative movement of the liquid droplet ejection head and the ejection receiving medium, by conveying at least one of the liquid droplet ejection head and the ejection receiving medium in a specified direction; and a droplet ejection control device which achieves a desired dot arrangement on the ejection receiving medium by causing the first and second liquids to be ejected from the liquid droplet ejection head toward the ejection receiving medium, in conjunction with the relative movement caused by the conveyance device, wherein an image is formed on the ejection receiving medium by means of droplets of the first and second liquids ejected from the first and second nozzles.
A compositional example of a liquid droplet ejection head in the image forming apparatus according to the present invention is a full line type inkjet head having a nozzle row in which a plurality of nozzles are arranged through a length corresponding to the full width of the ejection receiving medium.
In this case, a mode may be adopted in which a plurality of relatively short ejection head blocks having nozzles rows which do not reach a length corresponding to the full width of the ejection receiving medium are combined and joined together, thereby forming nozzle rows of a length that correspond to the full width of the ejection receiving medium.
A full line type inkjet head is usually disposed in a direction perpendicular to the relative feed direction (relative conveyance direction) of the ejection receiving medium, but modes may also be adopted in which the inkjet head is disposed following an oblique direction that forms a prescribed angle with respect to the direction perpendicular to the relative conveyance direction.
The “ejection receiving medium” in the image forming apparatus indicates a medium on which an image is recorded by means of liquid ejected from the liquid droplet ejection head (this medium may also be called a recording medium, ejection receiving medium, print medium, image forming medium, image receiving medium, or the like). This term includes various types of media, irrespective of material and size, such as continuous paper, cut paper, sealed paper, resin sheets, such as OHP sheets, film, cloth, a printed circuit board on which a wiring pattern, or the like, is formed by means of a liquid droplet ejection head, and an intermediate transfer medium, and the like.
The movement device for causing the ejection receiving medium and the liquid droplet ejection head to move relative to each other may include a mode where the ejection receiving medium is conveyed with respect to a stationary (fixed) head, or a mode where a head is moved with respect to a stationary ejection receiving medium, or a mode where both the head and the ejection receiving medium are moved.
According to the present invention, it is possible to achieve a high density arrangement of nozzles in a liquid droplet ejection head using a system which combines two liquids after ejection. Furthermore, in the present invention, it is possible to use an actuator such as a piezoelectric element in the first pressure generating devices and the second pressure generating devices and hence the freedom of selection of the ejection liquid is increased.
The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein:
The ink storing and loading unit 14 has ink tanks for storing the inks (liquid A) of K, C, M and Y to be supplied to the heads 12K, 12C, 12M, and 12Y, and the tanks are connected to the heads 12K, 12C, 12M, and 12Y by means of prescribed channels. The ink storing and loading unit 14 has a warning device (for example, a display device or an alarm sound generator) for warning when the remaining amount of any ink is low, and has a mechanism for preventing loading errors among the colors.
The treatment liquid storing and loading unit 15 has a treatment liquid tank for storing treatment liquid (liquid B) to be supplied commonly to the heads 12K, 12C, 12M, and 12Y, and this tank is connected to the heads 12K, 12C, 12M, and 12Y by means of prescribed channels. Furthermore, the treatment liquid storing and loading unit 15 has a reporting device (display device, alarm sound generating device) for issuing a report when the remaining amount of treatment liquid has become low.
In the present embodiment, one type of treatment liquid is supplied to the respective heads 12K, 12C, 12M and 12Y, but it is also possible to adopt a composition in which a plurality of different types of treatment liquids are used, with respect to the inks of different colors. In this case, the treatment liquid storing and loading unit 15 is provided with a mechanism for preventing the loading of the wrong type of treatment liquid.
More details are described below, but the heads 12K, 12C, 12M and 12Y comprise nozzles for ejecting liquid A (which correspond to the first nozzles and which may be referred to as “liquid A ejection nozzles” below, for the sake of convenience), and nozzles for ejecting liquid B (which correspond to the second nozzles and which may be referred to as “liquid B ejection nozzles” below, for the sake of convenience), these nozzles being arranged in a two-dimensional array, in such a manner that liquid A and liquid B can be deposited onto substantially the same position on the recording paper 16.
The ink (liquid A) used in the present embodiment is, for instance, colored ink including anionic polymer, namely, a polymer containing negatively charged surface-active ions. Furthermore, the treatment liquid (liquid B) used in the present embodiment is, for instance, transparent reaction promoting agent including cationic polymer, namely, a polymer containing positively charged surface-active ions.
When the liquid A and the liquid B are mixed, the insolubilizing reaction and/or fixing reaction of the ink coloring material proceeds due to a chemical reaction. Here the term “insolubilizing” includes a phenomenon whereby the coloring material separates or precipitates from the solvent, or a phenomenon whereby the liquid in which the coloring material is dissolved changes (coagulates) to a solid phase. Furthermore, the term “fixing” may indicate a mode where the coloring material is held on the surface of the recording medium, a mode where the coloring material permeates into the recording medium and is held therein, or a mode combining these states.
The reaction speed can be adjusted by regulating the composition of the liquid A and the liquid B, the concentration of the materials contributing to the reaction, or the like, and desired ink insolubilizing and/or ink fixing properties (fixing speed) can be achieved.
As for the supply system of the recording medium, in
In the case of a configuration in which a plurality of types of recording paper can be used, it is preferable that an information recording medium such as a bar code and a wireless tag containing information about the type of paper is attached to the magazine, and by reading the information contained in the information recording medium with a predetermined reading device, the type of recording medium to be used (type of medium) is automatically determined, and ink-droplet ejection is controlled so that the ink-droplets are ejected in an appropriate manner in accordance with the type of medium.
The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove the curl, heat is applied to the recording paper 16 in the decurling unit 20 by a heating drum 30 in the direction opposite from the curl direction in the magazine. The heating temperature at this time is preferably controlled so that the recording paper 16 has a curl in which the surface on which the print is to be made is slightly round outward.
In the case of the configuration in which roll paper is used, a cutter (first cutter) 28 is provided as shown in
The decurled and cut recording paper 16 is delivered to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a configuration in which an endless belt 33 is set around rollers 31 and 32 so that the portion of the endless belt 33 facing at least the nozzle face of the printing unit 12 and the sensor face of the print determination unit 24 forms a horizontal plane (flat plane).
The belt 33 has a width that is greater than the width of the recording paper 16, and a plurality of suction apertures (not shown) are formed on the belt surface. A suction chamber 34 is disposed in a position facing the sensor surface of the print determination unit 24 and the nozzle surface of the printing unit 12 on the interior side of the belt 33, which is set around the rollers 31 and 32, as shown in
The belt 33 is driven in the clockwise direction in
Since ink adheres to the belt 33 when a marginless print job or the like is performed, a belt-cleaning unit 36 is disposed in a predetermined position (a suitable position outside the printing area) on the exterior side of the belt 33. Although the details of the configuration of the belt-cleaning unit 36 are not shown, examples thereof include a configuration in which the belt 33 is nipped with cleaning rollers such as a brush roller and a water absorbent roller, an air blow configuration in which clean air is blown onto the belt 33, or a combination of these. In the case of the configuration in which the belt 33 is nipped with the cleaning rollers, it is preferable to make the line velocity of the cleaning rollers different than that of the belt 33 to improve the cleaning effect.
The inkjet recording apparatus 10 can comprise a roller nip conveyance mechanism, in which the recording paper 16 is pinched and conveyed with nip rollers, instead of the suction belt conveyance unit 22. However, there is a drawback in the roller nip conveyance mechanism that the print tends to be smeared when the printing area is conveyed by the roller nip action because the nip roller makes contact with the printed surface of the paper immediately after printing. Therefore, the suction belt conveyance in which nothing comes into contact with the image surface in the printing area, as shown in the present embodiment, is preferable.
A heating fan 40 is disposed on the upstream side of the printing unit 12 in the conveyance pathway formed by the suction belt conveyance unit 22. The heating fan 40 blows heated air onto the recording paper 16 to heat the recording paper 16 immediately before printing so that the ink deposited on the recording paper 16 dries more easily.
The print heads 12K, 12M, 12C and 12Y of the print unit 12 are full line heads having a length corresponding to the maximum width of the recording paper 16 used with the inkjet recording apparatus 10 (see
The print heads 12K, 12C, 12M and 12Y are arranged in color order (black (K), cyan (C), magenta (M), yellow (Y)) from the upstream side in the feed direction of the recording paper 16, and these respective heads 12K, 12C, 12M and 12Y are fixed extending in a direction substantially perpendicular to the conveyance direction of the recording paper 16.
A color image can be formed on the recording paper 16 by ejecting inks of different colors from the heads 12K, 12C, 12M and 12Y, respectively, onto the recording paper 16 while the recording paper 16 is conveyed by the suction belt conveyance unit 22.
By adopting a configuration in which the full line heads 12K, 12C, 12M and 12Y having nozzle rows covering the full paper width are provided for the respective colors in this way, it is possible to record an image on the full surface of the recording paper 16 by performing just one operation of relatively moving the recording paper 16 and the printing unit 12 in the paper conveyance direction (the sub-scanning direction), in other words, by means of a single sub-scanning action. Higher-speed printing is thereby made possible and productivity can be improved in comparison with a shuttle type head configuration in which a recording head reciprocates in the main scanning direction.
Although the configuration with the KCMY four standard colors is described in the present embodiment, combinations of the ink colors and the number of colors are not limited to those. Light inks, dark inks or special color inks can be added as required. For example, a configuration is possible in which inkjet heads for ejecting light-colored inks such as light cyan and light magenta are added. Furthermore, there are no particular restrictions of the sequence in which the heads of respective colors are arranged.
The print determination unit 24 shown in
The print determination unit 24 of the present embodiment is configured with at least a line sensor having rows of photoelectric transducing elements with a width that is greater than the ink-droplet ejection width (image recording width) of the heads 12K, 12C, 12M, and 12Y This line sensor has a color separation line CCD sensor including a red (R) sensor row composed of photoelectric transducing elements (pixels) arranged in a line provided with an R filter, a green (G) sensor row with a G filter, and a blue (B) sensor row with a B filter. Instead of a line sensor, it is possible to use an area sensor composed of photoelectric transducing elements which are arranged two-dimensionally.
A test pattern or the target image printed by the print heads 12K, 12C, 12M, and 12Y of the respective colors is read in by the print determination unit 24, and the ejection performed by each head is determined. The ejection determination includes detection of the ejection, measurement of the dot size, and measurement of the dot formation position.
A post-drying unit 42 is disposed following the print determination unit 24. The post-drying unit 42 is a device to dry the printed image surface, and includes a heating fan, for example. It is preferable to avoid contact with the printed surface until the printed ink dries, and a device that blows heated air onto the printed surface is preferable.
In cases in which printing is performed with dye-based ink on porous paper, blocking the pores of the paper by the application of pressure prevents the ink from coming contact with ozone and other substance that cause dye molecules to break down, and has the effect of increasing the durability of the print.
A heating/pressurizing unit 44 is disposed following the post-drying unit 42. The heating/pressurizing unit 44 is a device to control the glossiness of the image surface, and the image surface is pressed with a pressure roller 45 having a predetermined uneven surface shape while the image surface is heated, and the uneven shape is transferred to the image surface.
The printed matter generated in this manner is outputted from the paper output unit 26. The target print (i.e., the result of printing the target image) and the test print are preferably outputted separately. In the inkjet recording apparatus 10, a sorting device (not shown) is provided for switching the outputting pathways in order to sort the printed matter with the target print and the printed matter with the test print, and to send them to paper output units 26A and 26B, respectively.
When the target print and the test print are simultaneously formed in parallel on the same large sheet of paper, the test print portion is cut and separated by a cutter (second cutter) 48. The cutter 48 is disposed directly in front of the paper output unit 26, and is used for cutting the test print portion from the target print portion when a test print has been performed in the blank portion of the target print. The structure of the cutter 48 is the same as the first cutter 28 described above, and has a stationary blade 48A and a round blade 48B.
Although not shown in
Structure of the Head
Next, the structure of a head will be described. The heads 12K, 12C, 12M and 12Y of the respective ink colors have the same structure, and a reference numeral 50 is hereinafter designated to any of the heads.
As shown in
Furthermore, in the case of the present embodiment, the liquid B ejection nozzles 51B are arranged adjacently to the respective liquid A ejection nozzles 51A in such a manner that they are arranged on the same line in the sub-scanning direction. Taking the nozzle-to-nozzle distance between the liquid A ejection nozzle 51A and the liquid B ejection nozzle 51B adjacent to each other in the sub-scanning direction, to be LAB, and taking the distance in the sub-scanning direction between the mutually adjacent liquid A ejection nozzles 51A arranged in separate rows that are mutually adjacent in the sub-scanning direction (the distance between the rows of the liquid A ejection nozzles 51A) to be LAA, the relationship LAB<LAA is established, and the effective nozzle interval when projected to an alignment in the lengthwise direction of the head (main scanning direction) is P=LAA/tan θ. More specifically, the arrangement can be treated equivalently to a nozzle arrangement in which the respective nozzles 51A are arranged in a linear fashion at uniform pitch P, in the main scanning direction.
Here, an ejection element unit constituted by one liquid A ejection nozzle 51A and a corresponding liquid A pressure chamber 52A, and the like, is called an ink chamber unit 53A, and an ejection element unit constituted by one liquid B ejection nozzle 51B and a corresponding liquid B pressure chamber 52B, and the like, is called a treatment liquid chamber unit 53B.
Each of the pressure chambers 52A and 52B has an approximately square planar shape (the shape of the chamber when viewed in a direction perpendicular to the nozzle surface 50A, in other words, the planar shape of the pressure chamber when projected to a plane parallel to the nozzle surface 50A) (see
Furthermore, each of the pressure chambers 52A and 52B has an outlet port (nozzle flow channel connection port) connecting to a nozzle (51A or 51B), and a supply port 54A or 54B connected to the supply side, provided at respective ends of one diagonal line of the approximately square planar shape of the chamber.
The liquid A pressure chamber 52A is connected through the supply port 54A to a supply side common flow channel 55A (which corresponds to a first common flow channel and may be called “liquid A common flow channel” below, as and when necessary), and the liquid B pressure chamber 52B is connected through the supply port 54B to a supply side common flow channel 55B (which corresponds to a second common flow channel and may be called “liquid B common flow channel” below, as and when necessary).
The internal structure of the print head 50 is described now with reference to
The liquid A ejection nozzle 51A connecting to the liquid A pressure chamber 52 and the liquid B pressure chamber nozzle 51B connecting to the liquid B pressure chamber 52B are formed in the nozzle plate 111, which forms the bottommost surface of the head. Here, a “nozzle” is the final aperture portion from which liquid is ejected. Desirably, the nozzle size is designed to a diameter of approximately several tens μm, and to a length of several tens μm.
The nozzles 51A and 51B are formed to have shapes whereby the axes of the ejection ports are inclined respectively to a prescribed nozzle inclination angle, in order to restrict the direction of flight of the liquid droplets in such a manner that the two types of liquid ejected in a substantially simultaneous fashion from the nozzles land on substantially the same position on the recording medium.
Furthermore, the liquid A common flow channel 55A for supplying ink (liquid A) to the lower-positioned liquid A pressure chamber 52A and the liquid B common flow channel 55B for supplying a treatment liquid (liquid B) to the upper-positioned liquid B pressure chamber 52B are provided in the head 50, and the respective common flow channels 55A and 55B are arranged in respectively different layers corresponding to the pressure chambers 52A and 52B, as illustrated in
The liquid A pressure chamber 52A is connected to the liquid A common flow channel 55A via the supply port 54A, and it is also connected to the liquid A ejection nozzle 51A forming an ink ejection port via the first nozzle flow channel 57A. Similarly, the liquid B pressure chamber 52B is connected to the liquid B common flow channel 55B via the supply port 54B, and it is also connected to the liquid B ejection nozzle 51B forming the treatment liquid ejection port via the second nozzle flow channel 57B.
The liquid A common flow channel 55A is connected to an ink tank (not shown in
In
As stated previously, the liquid A ejection nozzles 51A and the liquid B ejection nozzles 51B are formed in the same nozzle plate 111, and the distance from the liquid A pressure chamber 52A to the liquid A ejection nozzle 51A (the length of the first nozzle flow channel 57A) is different to the distance from the liquid B pressure chamber 52B to the liquid B ejection nozzle 51B (the length of the second nozzle flow channel 57B).
In the case of the present embodiment, a liquid A having a relatively higher viscosity of the two types of liquid (i.e., A>B in viscosity) is supplied to the pressure chamber that is nearer to the nozzle plate 111 (liquid A pressure chamber 52A), and the liquid A is ejected from the liquid A ejection nozzle 51A, whereas the liquid B having a relatively lower viscosity is supplied to the pressure chamber that is further from the nozzle plate 111 (liquid B pressure chamber 52B), and the liquid B is ejected from the liquid B ejection nozzle 51B.
Furthermore, the respective shapes (cross-sectional area and length) of the first nozzle flow channel 57A and the second nozzle flow channel 57B are designed in such a manner that, when the first actuator 58A and the second actuator 58B are driven under prescribed common conditions, the ratio in the ejection volumes of the liquid A and the liquid B is a prescribed value.
In
A print head 50 having this structure can be fabricated by bonding the plurality of plate members (111 to 123) including a flow channel plate comprising a thin plate made of stainless steel, or the like, formed with holes and/or grooves, by means of etching, or the like. In this case, circular tubes of different radii are constituted by different flow channel plates.
In this way, since the holes in any one flow channel plate are of substantially uniform radius, processing is more straightforward compared to a case where holes of different radii are formed (processed by etching, or the like) in the same plate.
In the example in
The first nozzle flow channel plate 112 is a member which constitutes a portion of the first nozzle flow channel 57A and the thin tube of the second nozzle flow channel 57B. The second nozzle flow channel plate 113 is a member which constitutes a portion of the first nozzle flow channel 57A and the thick tube of the second nozzle flow channel 57B. The first common flow channel plate 114 is a member which constitutes the side walls of the liquid A common flow channel 55A, a portion of the first nozzle flow channel 57A, and a portion of the thick tube of the second nozzle flow channel 57B.
The first supply port plate 115 is a member which constitutes the supply port 54A (corresponding to the first supply ports), a portion of the first nozzle flow channel 57A, and a portion of the thick tube of the second nozzle flow channel 57B. The first pressure chamber plate 116 is a member which constitutes the side walls of the liquid A pressure chamber 52A and a portion of the thick tube of the second nozzle flow channel 57B. The first vibration plate 117 is a member which seals the upper face of the liquid A pressure chamber 52A (forming the ceiling thereof), and furthermore, also constitutes a portion of the thick tube of the second nozzle supply channel 57B. Furthermore, a first actuator 58A is fixed to the first diaphragm plate 117, in a position corresponding to each liquid A pressure chamber 52A.
The actuator avoiding plate 118 has a recess section 118A for ensuring a space in which the first actuator 58A is disposed, and it allows lamination of further layers above the first actuator 58A. Moreover, the actuator avoiding plate 118 constitutes a portion of the thick tube of the second nozzle flow channel 57B.
The third nozzle flow channel plate 119 is a member constituting a portion of the thick tube of the second nozzle flow channel 57B. The second common flow channel plate 120 is a member which constitutes the side walls of the liquid B common flow channel 55B and a portion of the thick tube of the second nozzle flow channel 57B. The second supply port channel plate 121 is a member which constitutes the second supply port 54B and a portion of the thick tube of the second nozzle flow channel 57B. The second pressure chamber plate 122 is a member which constitutes the side walls of the liquid B pressure chamber 52B. The second diaphragm plate 123 is a member sealing the upper surface of the liquid B pressure chamber 52B (forming the ceiling face thereof), and a second actuator 58B is fixed to the upper surface of the second diaphragm plate 123 in a position corresponding to the liquid B pressure chamber 52B.
In each of the actuators 58A and 58B, electrodes (not illustrated) are formed, and the electrodes are connected to a driving circuit (not illustrated), by means of wiring (not illustrated). It is possible to use the first diaphragm plate 117 and the second diaphragm plate 123 as the electrodes.
When a drive voltage is applied between the electrodes of the first actuator 58A, the first actuator 58A deforms, the volume of the liquid A pressure chamber 52A changes, and due to the consequent pressure change, a droplet of ink is ejected from the liquid A ejection nozzle 51A. After ejecting ink, new ink is supplied (replenished) to the liquid A pressure chamber 52A from the liquid A common flow channel 55A, via the supply port 54A.
Similarly, when a drive voltage is applied between the electrodes of the second actuator 58B, the second actuator 58B deforms, the volume of the liquid B pressure chamber 52B changes, and due to the consequent pressure change, a droplet of treatment liquid is ejected from the liquid B ejection nozzle 51B. After ejecting treatment liquid, new treatment liquid is supplied (replenished) to the liquid B pressure chamber 52B from the liquid B common flow channel 55B, via the supply port 54B.
By selectively driving the actuators 58A and 58B corresponding to the nozzles 51A and 51B to be used according to the image data that is to be recorded, it is possible to record a desired image.
As shown in
In a full-line head comprising nozzle rows that have a length corresponding to the entire width of the image recordable width of the recording medium, the “main scanning” is defined as printing one line (a line formed of a row of dots, or a line formed of a plurality of rows of dots) in the width direction of the recording paper (the direction perpendicular to the conveyance direction of the recording paper) by driving the nozzles in one of the following ways: (1) simultaneously driving all the nozzles; (2) sequentially driving the nozzles from one side toward the other; and (3) dividing the nozzles into blocks and sequentially driving the nozzles from one side toward the other in each of the blocks.
In particular, when the nozzles 51A, 51B arranged in a matrix such as that shown in
On the other hand, “sub-scanning” is defined as to repeatedly perform printing of one line (a line formed of a row of dots, or a line formed of a plurality of rows of dots) formed by the main scanning, while moving the full-line head and the recording medium relatively to each other.
In
Although not shown in
As shown in
When implementing the present invention, the structure of the head and the arrangement of the nozzles is not limited to that of the example illustrated. For example, instead of the composition of an integrated long matrix head illustrated in
Moreover, in the present embodiment, a method is employed in which ink or treatment liquid is ejected by means of the deformation of an actuator 58A or 58B, which is typically a piezoelectric element. However, in implementing the present invention, the method used for ejecting the ink or treatment liquid is not limited in particular, and instead of a piezo method, it is also possible to apply various types of methods, such as a thermal jet method where the ink or treatment liquid is heated and bubbles are caused to form therein by means of a heat generating body such as a heater, droplets of the ink or treatment liquid being ejected by means of the pressure of these bubbles.
Composition of Ink and Treatment Liquid Supply System
The ink tank 60A and the treatment liquid tank 60B may adopt a system for replenishing ink or treatment liquid by means of a replenishment opening (not illustrated), or a cartridge system wherein cartridges are exchanged independently for each tank, whenever the residual amount of ink or treatment liquid has become low. If the type of ink or the type of treatment liquid is changed in accordance with the type of application, then a cartridge based system is suitable. In this case, desirably, type information relating to the ink or treatment liquid is identified by means of a bar code, or the like, and the ejection of the ink or treatment liquid is controlled in accordance with the identified type. The ink tank 60A and the treatment liquid tank 60B in
As shown in
The inkjet recording apparatus 10 is also provided with a cap 64 as a device to prevent the nozzles 51A and 51B from drying out or to prevent an increase in the ink viscosity in the vicinity of the nozzles 51, and a cleaning blade 66 as a device to clean the nozzle face 50A. A maintenance unit including the cap 64 and the cleaning blade 66 can be relatively moved with respect to the head 50 by a movement mechanism (not shown), and is moved from a predetermined holding position to a maintenance position below the head 50 as required.
The cap 64 is displaced up and down relatively with respect to the head 50 by an elevator mechanism (not shown). When the power of the inkjet recording apparatus 10 is turned OFF or when in a print standby state, the cap 64 is raised to a predetermined elevated position so as to come into close contact with the head 50, and the nozzle face 50A is thereby covered with the cap 64.
The cleaning blade 66 is composed of rubber or another elastic member, and can slide on the ink ejection surface (surface of the nozzle plate) of the head 50 by means of a blade movement mechanism (not shown). If there are ink droplets, treatment liquid droplets or foreign matter adhering to the nozzle surface 50A, then the nozzle surface 50A is wiped by causing the cleaning blade 66 to slide over the nozzle surface 50A, thereby cleaning the nozzle plate surface. This wiping action is performed by sliding the cleaning blade 66 in the row direction of the nozzle arrangement illustrated in
During printing or during standby, if the use frequency of a particular nozzle has declined and the viscosity or the liquid (ink or treatment liquid) in the vicinity of the nozzle has increased, then a preliminary ejection is performed onto the cap 64, in order to remove the degraded ink or the degraded treatment liquid.
Furthermore, if air bubbles have mixed into the ink or treatment liquid inside the print head 50 (namely, into the pressure chambers 52A or the pressure chambers 52B), then the cap 64 is placed against the head 50, and the liquid (namely, the liquid containing air bubbles) inside the pressure chambers 52A and 52B is removed by suctioning by means of the suction pump 67, the liquid thus removed being conveyed to a collection tank 68. This suction operation is also carried out in order to remove degraded ink or degraded treatment liquid having increased viscosity (namely, hardened ink or treatment liquid), when ink or treatment liquid is loaded into the print head 50 for the first time, and when the print head 50 starts to be used again after having been out of use for a long period of time.
When a state in which ink is not ejected from the print head 50 continues for a certain amount of time or longer, the solvent in the vicinity of the nozzles evaporates and ink viscosity increases. In such a state, ink can no longer be ejected from the nozzles 51A even if the actuators 58A for driving ejection are operated. Similarly in respect of the nozzles 51B for ejecting treatment liquid, if the nozzles do not perform ejection for a long period of time, then it becomes impossible to eject the treatment liquid which has increased in viscosity. Therefore, before reaching such a state, the actuators 58A and 58B are operated toward an ink receptacle (here, as which the cap 64 is also serves) in a viscosity range that allows liquid to be ejected by the operation of the actuators 58A and 58B, and a “preliminary ejection” is thereby performed which causes the liquid in the vicinity of the nozzle of which viscosity has increased to be ejected. Furthermore, after cleaning away soiling on the surface of the nozzle plate by means of a wiper, such as the cleaning blade 66, provided as the cleaning device on the nozzle surface 50A, a preliminary ejection is also carried out in order to prevent mixing of foreign matter inside the nozzles 51A and 51B due to the rubbing action of the wiper. The preliminary ejection is also referred to as “dummy ejection”, “purge”, “liquid ejection”, and so on.
When bubbles have become intermixed in the nozzles 51A and 51B or the pressure chambers 52A and 52B, or when the liquid viscosity inside the nozzles 51A and 51B has increased over a certain level, the liquid can no longer be ejected by the preliminary discharge, and a suctioning action is carried out as follows.
More specifically, when bubbles have become intermixed in the ink inside the nozzles 51A and 51B and the pressure chambers 52A and 52B, the liquid can no longer be ejected from the nozzles 51A and 51B even if the actuators 58A and 58B is operated. Also, when the liquid viscosity inside the nozzles 51A and 51B has increased over a certain level, the liquid can no longer be ejected from the nozzles 51A and 51B even if the actuator 58 is operated. In these cases, a suctioning device to remove the liquid inside the pressure chambers 52A and 52B by suction with a suction pump, or the like, is placed on the nozzle face 50A of the head 50, and the liquid in which bubbles have become intermixed or the liquid of which viscosity has increased is removed by suction.
However, since this suction action is performed with respect to all the liquid in the pressure chambers 52A and 52B, the consumption amount of ink and treatment liquid is considerable. Therefore, a preferred aspect is one in which a preliminary discharge is performed while the increase in the viscosity of the liquid is small.
Description of Control System
The communication interface 70 is an interface unit for receiving image data sent from a host computer 86. A serial interface such as USB, IEEE1394, Ethernet, wireless network, or a parallel interface such as a Centronics interface may be used as the communication interface 70. A buffer memory (not shown) may be mounted in this portion in order to increase the communication speed.
The image data sent from the host computer 86 is received by the inkjet recording apparatus 10 through the communication interface 70, and is temporarily stored in the image memory 74. The image memory 74 is a storage device for temporarily storing images inputted through the communication interface 70, and data is written and read to and from the image memory 74 through the system controller 72. The image memory 74 is not limited to a memory composed of semiconductor elements, and a hard disk drive or another magnetic medium may be used.
The system controller 72 is constituted by a central processing unit (CPU) and peripheral circuits thereof, and the like, and it functions as a control device for controlling the whole of the inkjet recording apparatus 10 in accordance with a prescribed program, as well as a calculation device for performing various calculations. More specifically, the system controller 72 controls the various sections, such as the communication interface 70, image memory 74, motor driver 76, heater driver 78, and the like, as well as controlling communications with the host computer 86 and writing and reading to and from the image memory 74, and it also generates control signals for controlling the motor 88 and heater 89 of the conveyance system.
The program executed by the CPU of the system controller 72 and the various types of data which are required for control procedures are stored in the ROM 75. The ROM 75 may be a non-writeable storage device, or it may be a rewriteable storage device, such as an EEPROM. The image memory 74 is used as a temporary storage region for the image data, and it is also used as a program development region and a calculation work region for the CPU.
The motor driver (drive circuit) 76 drives the motor 88 in accordance with commands from the system controller 72. The heater driver (drive circuit) 78 drives the heater 89 of the post-drying unit 42 or the like in accordance with commands from the system controller 72.
The print controller 80 has a signal processing function for performing various tasks, compensations, and other types of processing for generating print control signals from the image data stored in the image memory 74 in accordance with commands from the system controller 72 so as to supply the generated print data (dot data) to the head driver 84. Prescribed signal processing is carried out in the print controller 80, and the ejection amount and the ejection timing of the ink and the treatment liquid are controlled via the head driver 84, on the basis of the print data. By this means, prescribed dot size and dot positions can be achieved.
The print controller 80 is provided with the image buffer memory 82; and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print controller 80. The aspect shown in
The head driver 84 drives the actuators 58A and 58B of the heads 50 of the respective colors 12K, 12C, 12M and 12Y on the basis of print data supplied by the print controller 80. The head driver 84 can be provided with a feedback control system for maintaining constant drive conditions for the print heads.
The image data to be printed is externally inputted through the communication interface 70, and is stored in the image memory 74. In this stage, the RGB image data is stored in the image memory 74.
The image data stored in the image memory 74 is sent to the print controller 80 through the system controller 72, and is converted to the dot data for each ink color by a half-toning technique, such as dithering or error diffusion, in the print controller 80. In this inkjet recording apparatus 10, an image which appears to have a continuous tonal gradation to the human eye is formed by changing the droplet ejection density and the dot size of fine dots created by ink (coloring material), and therefore, it is necessary to convert the input digital image into a dot pattern which reproduces the tonal gradations of the image (namely, the light and shade toning of the image) as faithfully as possible.
In other words, the print controller 80 performs processing for converting the inputted RGB image data into dot data for four colors, K, C, M and Y. The dot data generated by the print controller 80 is stored in the image buffer memory 82.
The head driver 84 generates drive control signals for the head 50 on the basis of the dot data stored in the image buffer memory 82. By supplying the drive control signals generated by the head driver 84 to the head 50, ink is ejected from the head 50. By controlling ejection of ink and treatment liquid from the heads 50 in synchronization with the conveyance velocity of the recording paper 16, an image is formed on the recording paper 16.
The print determination unit 24 is a block that includes the line sensor as described above with reference to
According to requirements, the print controller 80 makes various corrections with respect to the head 50 on the basis of information obtained from the print determination unit 24. Furthermore, the system controller 72 implements control for carrying out preliminary ejection, suctioning, and other prescribed restoring processes on the head 50, on the basis of the information obtained from the print determination unit 24.
In addition, the inkjet recording apparatus 10 according to this embodiment has an ink information reading unit 91, a treatment liquid information reading unit 92 and a media type determination unit 93. The ink information reading unit 91 is a device for reading in information relating to the ink type. More specifically, it is possible to use, for example, a device which reads in ink properties information from the shape of the cartridge in the ink tank 60A (a specific shape which allows the ink type to be identified), or from a bar code or IC chip incorporated into the cartridge. Besides this, it is also possible for an operator to input the required information by means of a user interface.
Similarly, the treatment liquid information reading unit 92 is a device for acquiring information relating to the type of treatment liquid. More specifically, it is possible to use, for example, a device which reads in treatment liquid properties information from the shape of the cartridge in the treatment liquid tank 60B (a specific shape which allows the liquid type to be identified), or from a bar code or IC chip incorporated into the cartridge. Besides this, it is also possible for an operator to input the required information by means of a user interface.
The media type determination unit 93 is a device for determining the type and size of the recording medium. This section uses, for example, a device for reading in information such as bar codes attached to the magazine 32 in the media supply unit 22, or sensors disposed at a suitable position in the paper conveyance path (a paper width determination sensor, a sensor for determining the thickness of the paper, a sensor for determining the reflectivity of the paper, and so on). A suitable combination of these elements may also be used. Furthermore, it is also possible to adopt a composition in which information relating to the paper type, size, or the like, is specified by means of an input via a prescribed user interface, instead of or in conjunction with such automatic determining devices.
The information acquired from the various devices, namely, the ink information reading unit 91, the treatment liquid information reading unit 92 and the media type determination unit 93 is sent to the system controller 72, where it is used to control ejection of the ink and treatment liquid (namely, to control the ejection volume and ejection timing), in such a manner that suitable droplet ejection is performed in accordance with the conditions.
Control of Ejection Driving
In the inkjet recording apparatus 10 having a composition of this kind, the supply of electrical power to the first actuators 58A and the second actuators 58B is controlled in a substantially simultaneous fashion to the pair of actuators 58A and 58B corresponding to the first nozzle 51A and the second nozzle 51B that are aligned adjacently in the sub-scanning direction. In other words, a drive waveform is supplied in parallel to the pair of actuators 58A and 58B that correspond to the first nozzle 51A and the second nozzle 51B that are aligned adjacently in the sub-scanning direction.
In this way, two types of liquid droplets 95A and 95B are ejected substantially simultaneously from the two nozzles 51A and 51B, as illustrated in
In this way, by using a common drive waveform for the actuators 58A and 58B, it is possible to simplify the driver circuit.
If it is necessary to be able to vary the mixture ratio of the liquid A and liquid B in accordance with the image data, or other conditions, then a composition which generates drive waveforms independently for the first actuator 58A and the second actuator 58B is adopted.
Next, a second embodiment of the present invention will be described.
The composition illustrated in
In the example shown in
According to the configuration illustrated in
A composition in which the liquid A and the liquid B are caused to land on the recording medium at a slight time difference apart is desirable in a case where an ink containing a coloring material (liquid A) and a treatment liquid (liquid B) containing a reaction promoting agent are used.
As shown in
In other words, the coloring material always lands on the reaction promoting agent and does not land directly on the recording medium. The coloring material landing on the droplet of the reaction promoting agent mixes with the reaction promoting agent upon landing, and immediately starts a fixing reaction. Thereby, it is possible to prevent bleeding of the dot created by the coloring material.
Even though the reaction promoting agent lands directly on the recording medium and permeates into the recording medium, since the reaction promoting agent does not contain any coloring material, it does not cause any problem in terms of giving rise to bleeding.
Next, a third embodiment of the present invention will be described.
Instead of the arrangement structure of the nozzles 51A and 51B, and the pressure chambers 52A and 52B described in
In the example in
In this case, a composition is adopted whereby the droplet ejection regions of two dots deposited by two liquid A ejection nozzles 51A-ik and 51A-im (where i is an integer, k=1, 3, 5, and m=k+1) at downstream positions are covered by dots deposited by one liquid B ejection nozzle 51B-ik located on the upstream side thereof in the conveyance direction of the recording medium.
The liquid B ejection nozzles 51B-11 previously deposits the dot 211B at a slight time difference before the dots 211A and 212A deposited by the nozzle 51A-11 and the nozzle 51A-12. The dot size DB of the dot 211B is set to value whereby the dot has a surface area to cover the droplet ejection region (dot coverage region) of the dot 211A and the dot 211B of liquid A.
Thereby, the deposited droplets forming dot 211A and dot 212A which contain coloring material react immediately with the reaction promoting agent in dot 211B, and hence a fixing reaction starts.
In the dot arrangement shown in
Furthermore, in this third embodiment, droplet ejection is controlled in such a manner that a dot 211B is deposited only when at least one of the dots 211A and 212A is to be deposited. By omitting unnecessary formation of dots of liquid B which do not contribute to a reaction, it is possible to reduce the consumption of liquid B.
Next, a fourth embodiment of the present invention will be described.
The embodiment shown in
A liquid A ejection nozzle 51A-ij and a liquid B ejection nozzle 51B-ij are aligned in mutually adjacent positions in the sub-scanning direction (the conveyance direction of the recording medium).
This composition is similar to the embodiment shown in
Next, a fifth embodiment of the present invention will be described.
As shown in
As described previously, wiping is performed by sliding the cleaning blade 66 in the row direction of the nozzle arrangement (the lengthwise direction of the print head). The liquid adhering to the nozzle surface 50A moves over the nozzle surface 50A due to the wiping action, but if two different types of liquid enter into the nozzle apertures, then a combined reaction of the liquids will occur.
In order to avoid situations of this kind, the grooves 240 are provided as a device for preventing mixture of the liquids, (in other words, a device for restricting the range of movement of the liquids), between the liquid A ejection nozzles 51A and the liquid B ejection nozzles 51B. Instead of the grooves 240 or in conjunction with same, it is also possible to provide projection-shaped dividing members (not illustrated), for example.
In the foregoing embodiments, the reaction promoting agent has been described as an example of a treatment liquid, but a mode is also possible in which a permeation retarding agent is used instead of a reaction promoting agent. The permeation retarding agent has a function of delaying the progress of permeation of the ink into the recording medium, by combining with the ink (liquid A) containing coloring material. This is suitable for use in the case of a recording medium such as standard paper, in which the liquid permeates while diffusing in the planar direction within the medium, and which is therefore liable to bleeding.
Moreover, in the foregoing explanation, an inkjet recording apparatus has been described as one example of an image forming apparatus, but the scope of application of the present invention is not limited to this. For example, the liquid droplet ejection head according to the present invention may also be applied to a photographic image forming apparatus in which developing solution is applied onto a printing paper by means of a non-contact method. Furthermore, the scope of application of the liquid droplet ejection head according to the present invention is not limited to an image forming apparatus, and the present invention may also be applied to various other types of apparatuses which spray a processing liquid, or other liquid, toward an ejection receiving medium by means of an ejection head (such as a coating device, wiring pattern printing device, or the like).
It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.
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